RTEP2015
IOP Publishing
IOP Conf. Series: Materials Science and Engineering 110 (2016) 012075 doi:10.1088/1757-899X/110/1/012075
The Study of Radiolysis of Ba(NO3)2 by ESR
V Kh Pak1, E P Dyagileva2, S Yu Lyrshchikov3, M B Miklin1, V A Anan’ev1
1
Kemerovo State University, Krasnaya str, 6, Kemerovo, 650043, Russia,
Kemerovo State Medical Academy, Voroshilov str, 22a, Kemerovo, 650029, Russia
3
National Research Tomsk Polytechnic University, Institute of Power Engineering, 30, Lenin Avenue,
Tomsk, 634050, Russia
2
E-mail: [email protected]
Abstract. Irradiation of Ba(NO3)2 γ-rays at 308 K at increasing absorbed dose creates several
new PC: 1, 2, 3, X. All of these are characterized by almost isotropic g-factor. Comparison of
the observed parameters with literature data allows us to identify the PC as follows: 1 - O3–, 2 O–. PC 3 and X presumably attributed to the complex centers [NO 2...O2] or [NO2–...O–...O2]
and [O–...O2], respectively.
1. Introduction
The paramagnetic centers (PC) NO2, On– (n = 1-3), and F-centers were found under the radiolysis of
crystalline Ba(NO3)2 at 300 K [1, 2]. At 77 K PC NO3, ONOO, and NO32– were found [3-6]. The diamagnetic products peroxynitrite ONOO– and nitrite NO2– were formed by radiolysis of crystalline
Ba(NO3)2 at 300 K [7-9].
X-ray irradiation at 300 K (absorbed dose ~ 5∙103-5∙104 kGy was estimated by us from the data represented in [1]) results in ESR spectrum due to F-centers, O2–, O3–, and NO2 [1]. The latter was registered at 85 K only. The annealing of F-centers was observed at room temperature, and at 358 K they
completely decay within 3-5 minutes. This process simultaneously results in the increasing of O2– and
O3– concentration.
A γ-ray irradiation at 300 K (absorbed dose ~ 1000 kGy) results in ESR spectrum due to O–, O3–,
and unidentified paramagnetic center [2]. The former is stable up to 570 K, the latter is annealed at
330-350 K. The ozonide ion decay under the heating of irradiated sample up to 440-480 K. Thus, there
are the difference both PC observed in [5,6] and they thermal stability. It may be connected with the
values of absorbed dose.
The goal of this investigation is to study the accumulation of PC under γ-irradiation of Ba(NO3)2 at
308 K.
2. Experimental
Single crystals of Ba(NO3)2 were grown by slow evaporation of aqueous solution of "reagent grade"
salt. The samples were irradiated with 60Co -rays at 308 K. The dose rate 0.69 Gy/s was measured
with a Fricke dosimeter, assuming the radiation chemical yield of Fe3+ to be equal to 15.6 (100 eV)-1.
The absorbed dose was calculated using the mass energy absorption coefficients. ESR spectra were
registered by X-band spectrometer Bruker EMX Micro 6/1 at 300 К. The angular dependences of ESR
spectra were constructed with using DPPH (g = 2.0036). The value of g-tensor were determinate with
accuracy ± 0.0007.
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RTEP2015
IOP Publishing
IOP Conf. Series: Materials Science and Engineering 110 (2016) 012075 doi:10.1088/1757-899X/110/1/012075
3. Results
ESR spectrum due to all of observed PC was registered under irradiation by dose 400 kGy only (Fig.
1). Eigenvalues of PC’ g-tensor represent in Table 1 were calculated from dependencies of the ESR
spectra for different crystal orientation in the magnetic field. As seen, all of observed PC have almost
isotropic g-tensors while in the earlier studies they have axial or rhombic symmetry (Table 1).
From our calculated g-factors values and published data it is follows that PC 1 is radical O3–, the
PC 2 and PC X are radical O–. A g-factor of PC 3 corresponds to radical NO2, but its hyperfine structure differ from the one for NO2 in other matrix. For the latter case, the assignment is clearly selfexplanatory, because we observed only two from three lines (low intensity of spectrum is not possible
to observe the remaining line) and the hyperfine splitting does not match the known values for this
radical.
Irradiation by the doses from 10 to 150 kGy of barium nitrate single crystals results in the ESR spectrum due to ion-radical O3 – only. It is stable at 300 K.
Figure 1. Spectrum ESR γ-irradiated (400 kGy) Ba(NO3)2.
Figure 2. Accumulation radical O3– at γ-radiolysis of Ba(NO3)2.
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RTEP2015
IOP Publishing
IOP Conf. Series: Materials Science and Engineering 110 (2016) 012075 doi:10.1088/1757-899X/110/1/012075
Table 1
Radical
X
1
2
3
Eigenvalues of g- tensors for PC Х, 1, 2, and 3.
gxx
gyy
gzz
gave
2.0453
2.0448
2.0451
2.0451
2.0218
2.0170
2.0172
2.0190
2.0110
2.0107
2.0128
2.0115
1.9889
1.9798
1.9761
1.9816
The accumulation of O3– up to 15 kGy is almost linearly (Fig. 2). The value of initial radiationchemical yield of O3– is equal to 0.016 rad/100 eV. Increase of the irradiation dose results in decrease
of the rate of O3– formation and at the absorbed dose higher than 80-100 kGy the concentration become constant (1.6 1017 rad/g).
Irradiation of barium nitrate by dose > 120 kGy results in ESR spectrum due to O–, and when dose
> 1400 kGy one can be see center X (Fig. 3). At dose > 350 kGy in the ESR spectrum appears two
small signals assignment as 3 in Fig. 1. The increase of the absorbed dose results in the decrease of its
rate of formation X, but the accumulation of the paramagnetic center observes up to ~ 500 kGy.
Figure 3. Accumulation radical X at γ-radiolysis of Ba(NO3)2.
The consistent irradiation of single crystal Ba(NO3)2 at 308 K to 40kGy and then at 77 to 1kGy result
to appearance in ESR spectrum lines belonging to the radical NO2, located in four magnetically nonequivalent positions (Fig. 4).
4. Discussion
Comparison of the parameter of g-tensor observed radicals with literature data allows us to identify the
PC as follows: 1 - O3, 2 - O–. PC 3 and X presumably attributed to the complex centers [O– ... O2] and
[NO2 ... O2] or [NO2– ... O– ... O2], respectively.
At γ-irradiation is forming complex "cell" centers [NO2–...O] or [NO2–...O2...NO2–]. It is supposed
that initially analogical “cell” pairs are formed in the volume and on the surface of Ba(NO3)2 at photolysis [10] too.
The collapse of complex defects may result in the "free" radical O–. Interaction O– with a molecule of
oxygen O2 leads to O3–. Presumably, at low absorbed doses, is forming centers of the type [NO2–
...O2...NO2–] and radicals are formed O3– only. Then, in the ESR spectra appear free radicals O–.
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RTEP2015
IOP Publishing
IOP Conf. Series: Materials Science and Engineering 110 (2016) 012075 doi:10.1088/1757-899X/110/1/012075
Next capture free electrons and holes on the above-mentioned complex radiation defects can lead to
radical products of transformation of these particles. Thus, paramagnetic particles can be formed from
[NO2–...O–] or [NO2–...O2] to create free oxygen radicals or complex products, for example:
Figure. 4. The ESR spectrum of Ba(NO3)2 γ-irradiated at first
at 300K (40 kGy) and then at 77 K (1 kGy), measured at 77K.
[NO2–…O] + e → NO2– + O–
[NO2–…O] + e → [NO2–…O–]
Formation of simple paramagnetic centers On– output due to the possibility of diffusion such a radical in the interstitial space.
[NO2–…O2] + O– → NO2– + O3–
Capture free holes can be result in formation radical NO2
[NO2–…O] + h → NO2 + O
Acknowledgments
This works was supported state assignment of Ministry of Education and Science of Russian Federation No 2015/64.
References
[1]
[2]
Tagaya K 1985 J. Appl. Phys. 2 75
El'vikh L P, Gorbovitskaya T I, Bugaenko L T and Tiliks Yu E 1977 High Energy Chem.
11 348
[3] Harrinson L G, Ng Hok Nam H N1973 J. Chem. Soc. Faraday Trans I 69 1432
[4] Ždansky K, Šroubek Z 1965 Phys. Stat. Sol. 10 571
[5] Kikuchi R, Nogaito T, Tagaya K, Matsumoto K 1967 Mem. Inst. Sci. Ind. Res. 24 53
[6] Bannov S I, Miklin M B1997 High Energy Chemistry 31 233
[7] Anan’ev V, Kriger L, Miklin M 2015 IOP Conf. Series: Mater. Sci. Engineer. 80 012023
[8] Chen T-H, Johnson E R 1962 J. Phys. Chem. 66 2249
[9] Kulkarni S P, Garg A N 1986 Journal of Radioanalytical and Nucl. Chem. 98 65
[10] Miklin M B, Ghyngazov S A, Pak V Kh, Anan’ev V A 2016 J. Photochem. Photobiol. A 315 94
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